1. Field of the Invention
The present invention relates generally to a digital data recording/reproducing apparatus, and more particularly to a digital data recording/reproducing apparatus for recording/reproducing digital data compressed in accordance with a variable bit rate encoding scheme.
2. Description of Related Background Art
At present, widespread video and audio media include a laser disk (LD), a VHS video and so on in the analog scheme, and a mini-disk (MD), a compact disc (CD) and so on in the digital scheme. On the other hand, as package media for the next generation, technological developments have been vigorously advanced for practical use of a rewritable digital versatile disk (DVD-R/W) which enables recording and reproduction of images and sound with high quality for a long time. In a recording method using DVD-R/W, information data pieces such as a movie, audio and so on can be recorded on a disk in high density. Image data are recorded/reproduced in accordance with a highly efficient encoding scheme such as MPEG2, while audio data are recorded/reproduced in accordance with compression schemes such as PCM, AC3 or the like. In the following, a collection of data such as a full program, a full movie or the like is called an “information data piece”, and data which includes one or a plurality of information data piece is called an “information data group”.
In a recording/reproducing scheme for a conventional recordable and erasable digital data recording/reproducing apparatus, for example, MD, an audio information data piece is again divided into a plurality of subpieces, each of which is given address information that is relied on to display a playing time and to search for particular data. Stated another way, since MD has a fixed compression ratio for audio data, an actually required time for reproduction can be unitarily calculated by multiplying the amount of data by a playing time per unit time. Therefore, a data region is comprised only of audio data and does not include time information on reproduction.
However, as a method of extending a recording time for images, DVD-R/W has employed a “variable bit rate coding: VBR” which changes the amount of codes in accordance with a change in the amount of information in an image in place of a conventional “constant bit rate coding: CBR”, so that an actually required time for reproduction cannot be calculated directly from the amount of compressed data. In other words, it is not possible to use a conventional approach of deriving a playing time from the address of a reproduced position. Also, while DVD-R/W has a feature of providing an erasable recording medium, recorded time information becomes discontinuous if the user erases a desired region or the like, thereby causing impediments to a time search, a playing time display, and so on.